A method for calibrating seismic stacking velocities against velocities from well measurements has been developed to quantitatively assess the validity of stacking velocities in the vicinity of boreholes and to improve quality of stacking velocities for use in regional depth conversion of interpreted seismic horizons. Accurate depth conversion of seismic interpretation is vital for use as constraints in gravity modelling and in other basin modelling tasks. Examples of this methodology are given for the northern Perth Basin, Australia. The suggested workflow for calibrating seismic stacking velocities against well velocities in a simplified form is as follows: 1. Check each velocity dataset for errors 2. Modify the datum of each dataset to the sea floor 3. Convert all datasets to two-way time and depth domain 4. Resample all velocity datasets to the same two-way time intervals 5. Cross plot stacking velocity depths near a well site with corresponding well depths for equal two-way times 6. Fit a linear polynomial to this cross-plot (higher order polynomials were tried also), and determine calibration coefficient from the gradient of the polynomial. 7. Grid calibration coefficients 8. Multiply depths derived from stacking velocities by calibration coefficient grid An assessment of depth conversion errors relative to wells shows that this methodology improves depth conversion results to within ±50 m down to the maximum well depth analysed (3.5 km below sea floor); this depth uncertainty translates into a modelled gravity anomaly error of about ±20 gu, which is acceptable for regional scale gravity modelling.

Stacking velocities for surveys 1001 (Shell Petrel) and 1053 (Esso R74A) over the Bremer and Denmark Sub-basins were analysed for depth and time.

Despite long history of studies the Wallaby Plateau offshore Western Australia remains a controversial feature. Analysis of interval seismic velocities from Geoscience Australia's 2008/09 seismic survey 310 in conjunction with seismic reflection interpretation provides new insights into the geology of the Plateau. Seismically distinctive divergent dipping reflector sequences (DDRS) have been identified. The seismic character of the DDRS is similar to seaward dipping reflector sequences (SDRS) of inferred volcanic composition. Initial analysis of seismic velocity profiles indicated affinities between the DDRS packages and known sedimentary strata in the Houtman Sub-basin. Effect of water loading on seismic velocities is commonly ignored in offshore studies. However, direct comparative analysis of interval velocity patterns between areas of significantly different water depth requires various water pressure related changes in velocity to be accounted for. There are controversies in methodology and application of water depth adjustment to seismic velocities, and presentation of velocity models as function of pressure rather than two-way time, or depth emerges as a possible solution. Water depth adjustment of seismic velocities analysed in our study reduces distinction between SDRS, DDRS and sedimentary strata such that discrimination between volcanic and sedimentary strata in DDRS or SDRS is equivocal. A major uncertainty of this interpretation is due to a lack of the reference velocity model of SDRS and DDRS investigated globally.

Geoscience Australia acquired the Canning Coastal Deep Crustal Seismic Survey in 2014. The survey involved the acquisition of seismic reflection and gravity data along two traverses, 14GA-CC1 (562km) and 14GA-CC2 (143km) between Port Hedland and Derby, WA. The purpose of the survey was to image the crustal architecture of the geology underlying the Canning Basin and its relationship to the boundaries between the crystalline hard rock areas of the North (Kimberley) and West Australian (Pilbara) cratons. As well as establishing the subsurface extent of the Canning Basin and the extent and nature of its sub-basins and troughs. The project was collaboration between the Geological Survey of Western Australia and Geoscience Australia with funding from the Western Australian Royalty for Regions Scheme. Raw data for this survey are available on request from clientservices@ga.gov.au

Towa.:ccis the end of 1960 , the Bureau. of Mineral Resources, Geology and Geophysics made a brief seismic survey in the Winton area of Queensland to resolve an apparent contradiction between the interpretations of gravity and aeromagnetic results previously obtained in the area. Gravity and aeromagnetic results both suggested the occurrence of a large fault or fault zone about 20 miles north-west of Winton, but the gravity and aeromagnetic interpretations differed regarding the direction of throw of the fault. A nine-mile seismic reflection traverse was surveyed across the supposed fault. The seismic results indicate the presence of a large fault or monoclinal fold with dowthrown side nouth-wast as suggested by the gravity values and also a smaller fault or monocline about two miles south-east with downthrown side south-east. The variations in thckness of Mesozoic rocks caused by these features were insufficient to explain the observed Bouguer gravity anomaly values, but the seismic results left open the possibilitues that there may be a considerable thickness of pre-Mesozoic sedimemts north-west of the main monocline or fault. It is postulated that the steep gravity gradient observed may be due to a large fault whose main movement took place in pre-Mesozoic times. Indications are that there is 5000 to 6000 ft of Mesozoic sediments in tha area.

Seismic refraction velocities were measured in the Archaean or crystalline basement rocks at Mount Davies (SA) and Giles (WA) where the rocks are near the surface. Refraction velocities were measured in the Proterozoic outcrops of the Rawlinson Range and Lake Hopkins. Refraction velocities were measured in the Palaeozoic and Mesozoic rocks at Lake Christopher, and in the Mesozoic rocks at Iragana Turnoff. Those velocities were used as a basis for a suggested correlation between refractors recorded at traverses between Signpost and Mount Beadell. Reflection tecniques, as tried 9 yielded fair reflections at Mount Beadell, and doubtful reflection alignments at trig. point NMF 19. It is likely that the sedimentary basin shows an increasing thickness of sediments from Signpost to Mount Beadell, At Mount Beadoll there is at least 6000 ft of apparently post-Proterozoic sediments. The thickness and degree of metamorphism of Proterozoic ratio below this have not been determined. Present evidence suggests an area of uplift under Lake Breaden.

During 1961 in the southern part of the Surat Basin a seismic party from the Bureau of Mineral Resources surveyed two main traverses by means of seismic reflection and refraction methods; the first was in an east-west direction between Yelarbon and St George and the second was in a north-south direction between Meandarra and Nome. The main purposes of the survey were to find whether the Bowen Basin Permian sediments extend as far south as the latitude of Goondiwindi and whether the Bowen Basin in Queensland and the Sydney Basin in New South Wales formed a continuous region of sedimentation during the Permian period. The east-west seismic traverse indicated a trough of sediments of greatest thickness,tabout 14,800 ft beneath Toobeah; the trough is bounded on the eastorn side at Goondiwindi by a fault down-thrown more than 7000 ft to the west and is bounded on the western side by a series of step.-faults beneath Bungunya and Talweod. The results along the north-south traverse indicated that the trough beneath Meandarra, which represents the southern extension of the Bowen Basin, continues south to Toobeah. The nature of the link, if any, between the Bowen Basin and the Sydney Basin was not established. On the eastern side of the Surat Basin, seismic results indicated that the rocks beneath the Mesozoic sediments are stratified and probably metamorphic. A shelf area between Talweod and St George has about 6000 ft of sediments above a Drobablo metamorphic 'basement'. An anticlinal structure with a dip-reversal of about 1000 ft throw was located between Goondiwindi and Toobeah.

The Bureau of Mineral Resources Seismic Party No. 2 conducted a survey from 15th May to 25th August 1961 in the Amadeus Basin. Reflection and refraction traverses were shot at intervals, along or near the Alice Springs/Port Augusta railway line, from Polhill in the north to Finke in the south. In broad terms the object of the survey was to obtain across the Amadeus Basin a north-south seismic cross-section that would aid in investigating the stratigraphic cross-section and structural relations especially on the southern margin of the Basin. Access and drilling problems caused the progress of the survey to be slow. The statistics of the operation are included in three appendices. During the course of the seismic survey, the Bureau also made gravity surveys covering the area; gravity-meter readings were made along all seismic traverses.

The Undilla Basin, in north-western Queensland, is a small sedimentary basin containing Cambrian limestones which adjoin the widespread but undated CamoowJal Dolomite to the West. In the latter part of 1961 the Bureau of Mineral Resources, Geology and Geophysics did a brief reconnaissance seismic survey lasting about seven weeks in the Undilla Basin. This Record describes briefly the work done and results obtained. The occurrence of limestone near the surface throughout the basin presented difficult problems in the application of the reflection and refraction seismic methods but some progress was made towards the solution of these problems.

The Bureau of Mineral Resources'No. 2 seismic party conducted a Survey over the Palm Valley Anticline 80 miles west of Alice Springs, from 2nd November to 22nd November 1961. The seismic reflection method showed (a) the anticlinal structure existed at depth and (b) at the northern end of the main north-south traverse in the Missionary Plains north-dipping reflections were recorded from about 2500-ft depth. A shallow refractor was recorded in which the velocity Was 17,800 ft/sec. This refractor, which could not be positively identified, prevented, any useful deeper refraction information being recorded.